The effect of anticoagulant (heparin vs EDTA) on chemokine induced CD11b upregulation on neutrophils, eosinophils, and monocytes in human whole blood was determined. For most of the chemokines (IL-8, GRO-alpha, MCP-1, MIP-1 alpha) the difference in the response of leukocytes in EDTA anticoagulated blood vs those in heparinized blood was the degree of their maximal response, with a slightly higher maximal increase in CD11b expression usually seen in cells from EDTA anticoagulated blood. Two chemokines were exceptions to this: RANTES and MIP-1 beta. RANTES is considered to be a stimulator of monocytes and eosinophils and not of neutrophils. As expected, neutrophils in heparinized whole blood did not respond to RANTES; however, neutrophils in EDTA anticoagulated blood had a significant increase in CD11b when exposed to high concentrations (1 microM) of RANTES. RANTES-induced CD11b expression on monocytes and eosinophils in these samples were the same in either heparin or EDTA. In EDTA anticoagulated blood, MIP-1 beta did not elicit a response in either monocytes, eosinophils or neutrophils; however, in heparinized blood, all three cell types increased CD11b expression upon exposure to 1 microM MIP-1 beta.